1. Field of the Invention
This invention relates generally to bodies which are designed to move through a fluid, such as air or water, and, more particularly, to techniques for the reduction of drag on said bodies by providing the bodies with structure on their rear surface.
2. Description of the Related Art
A great deal of effort has been exerted in the past to find ways of reducing the fluid drag which is encountered when bodies such as motor vehicles, water craft, aircraft, projectiles, and the like, move through fluid such as air or water in the course of their use. The major concentration of aerodynamic research has been to alter the structure of the various bodies to achieve streamlining, or in the alternative, to provide the top, bottom or side surfaces of the body with various kinds of corrugations, troughs, ridges, and the like, which are designed to create turbulence in the boundary layer and thus reduce drag.
Thus, U.S. Pat. No. 2,261,558, issued on Nov. 4, 1941, to Orloff; U.S. Pat. No. 2,800,291, issued on Jul. 23, 1957, to Stephens; U.S. Pat. No. 2,899,150, issued on Aug. 11, 1959, to Ellis; and U.S. Pat. No. 4,650,138, issued on Mar. 17, 1987, to Grose; show various grooves, depressions, and the like in the leading or top surfaces of aircraft wings, designed to act as drag reducers.
Similarly, U.S. Pat. No. 4,284,302, issued on Aug. 18, 1981, to Drews; U.S. Pat. No. 4,180,290, issued on Dec. 25, 1979 to Drews; U.S. Pat. No. 4,776,535, issued on Oct. 11, 1988, to Paterson; U.S. Pat. No. 4,789,117, issued on Dec. 6, 1988, to Paterson; U.S. Pat. No. 4,813,633, issued on Mar. 21, 1989, to Werle; and British Patent 453,086, issued Sep. 4, 1936, to Staunton; show similar treatment of the leading, top and side surfaces of motor vehicles, such as cars and trucks.
There is less evidence of efforts to achieve drag reduction by modifying the back vertical surfaces of vehicles, craft, projectiles or other bodies which move through a fluid environment. Some activity along this line is shown in U.S. Pat. No. 4,702,509, issued on Oct. 27, 1987 to Elliott; U.S. Pat. No. 4,861,093, issued on Aug. 29, 1989, to Chapman; Russian Patent 927,616, issued May 15, 1982; and U.S. Pat. No. 4,682,808, issued on Jul. 28, 1987, to Bilanin, which show the addition of streamlining airbags, or flow-through channels, or other forms of bulky vanes or panels to rear vertical surfaces. However, those references are generally applicable to tractor-trailers or other motor vehicles having add-on structures which are so large that they must be removed and stored when access to the interior of the vehicle is required. These structures also can provide an appreciable contribution to the overall length of the motor vehicle.